The present invention relates to portable handheld induction heaters. Such induction heaters have a variety of uses, such as in the automotive aftermarket for vehicle repair and maintenance, i.e., selectively heating automotive metallic and adjacent components, and removing components bonded or attached to metallic surfaces (e.g., fasteners), or removing structure attached by means of adhesive (e.g., glass). Other uses for such induction heaters include similar, maritime uses, industrial uses such as heating rods to bend them in a fabrication process, annealing ammunition cartridges, etc.
Portable handheld induction heaters useful in the automotive aftermarket are known. See for example, Applicant's U.S. Pat. Nos. 6,563,096 and 6,670,590, titled “Eddy Current/Hysteretic Heater Apparatus And Method Of Use” and “Eddy Current/Hysteretic Heater Apparatus,” respectively, each of which is incorporated by reference in its entirety. Applicant's pending U.S. Ser. No. 14/065,844, filed Oct. 29, 2013, titled “Portable Induction Heater,” and Ser. No. 14/330,429 filed Jul. 14, 2014, titled “Induction Heater Coil Accessory,” disclosing, e.g., handheld induction heaters which can run on power supplied at 12-24 volts, as well as 110-240 volts, and disclosing alternative forms of work coils, respectively, are each hereby incorporated by reference in their entirety.
Induction heaters may be air-cooled or water-cooled. The present invention concerns air-cooled induction heaters. Three main components of a modern induction heater include the power unit (power inverter), optional output/isolation transformer and the coil (inductor). Induction heating is a non-contact method of heating a conductive body by utilizing a strong magnetic field. Induction heaters may incorporate a coil directly fed from the electricity supply. The power unit/inverter is used to take the supply/mains frequency and increase it to a higher frequency, typically anywhere between 1-400 kHz. Typical power output of a unit system may be about 1-500 kW. The work head/transformer may include a combination of capacitors and transformers used to mate the power unit to the work coil. The work coil/inductor is used to transfer the energy from the power unit and work head to the work piece. Inductors of the type of the present invention consist of a simple wound solenoid with a number of turns of copper tube wound around a mandrel.
To work properly, the coil must be placed in close proximity to the work piece (e.g., a nut to be loosened). This can be difficult in tight or difficult to access areas and/or where there are closely adjacent surfaces to the work piece, which the operator does not wish to heat or damage.
A conventional coil configuration used for handheld induction heaters utilizes round conductor wire (e.g., copper), which may be bent into various coil shapes, and which typically have two lead wires or “legs” 32 which may be detachably connected to the induction heater. Work coils typically have circular cross-sections. However, the round wire of work coils may be flattened to provide work coils with semi-circular and rectangular cross-sectional geometries, as has been recently disclosed (see Applicant's U.S. Ser. No. 14/330,429, referenced above).
In the past, the ends or legs of work coils have been attached to the head of a portable induction heater using thumb screws. Thumb screws take a relatively long time to change the work coil, i.e., the user must loosen the two thumb screws, remove the coil legs, insert the coil legs of a different work coil (such as one of a different size and/or shape), and re-tighten the two thumb screws. Thumb screws can loosen over time, as the induction heater is used. The user may not be aware that loosening has occurred, until various conditions occurs, such as: (a) excessive heat develops in the heat dissipating terminal (“HDT”), which can melt the thumb screw cap; or (b) a loose coil creates sparks, which can damage electronics in the induction heater.
Accordingly, it would be advantageous to provide a faster, more reliable method for attaching and detaching the work coil legs to an induction heater. It would also be advantageous to provide a secure attachment device and method which works with work coil legs of different cross-sectional geometries, including circular, semi-circular and rectangular geometries.